Most tire and rim assemblies require balancing to prevent vibration within the vehicle while it is in motion. One method of balancing tire and rim assemblies involves rotation of the assembly on a computerized balancing machine to determine the location and size of weights necessary to obtain balanced rotation. Lead weights of the determined size are then clamped to the assembly at the indicated points to complete the balancing procedure. There are other similar `fixed weight` systems known for tire balancing. Some disadvantages of this type of system are that tire balancing equipment is expensive, tire balancing requires a skilled operator and is time consuming, and tires must be rebalanced at regular intervals due to effects of varying tread wear.
Continuous self-balancing systems overcome many of the disadvantages of the above fixed weight systems. Continuous self-balancing systems use the principle that free flowing materials contained in a vessel in rotation will seek a distribution in balance about the centre of rotation and will tend to offset, by mass damping, any imbalance inherent in the vessel. The effectiveness of a dynamic self-balancing system is dependent in part on the ease with which balancing material can move within the vessel to positions that offset points of imbalance.
One method for applying the self balancing principle was disclosed in the International Publication Number WO 95/00347, by Heffernan et al. In this PCT patent application, a free flowing balancing material is placed directly within a pneumatic tire to obtain a dynamic balance while the wheel is in rotation. The balancing material comprises a mixture of small dense beads and larger less dense beads which distribute within the tire under centrifugal forces to dampen vibration. The beads of the mixture are of a substantially rounded shape to reduce friction and improve the mobility of the material during balancing.
As the tire rotates, the small dense beads are forced against the tire casing to fill in imperfections or voids on the tire wall to form a smooth lining allowing the larger less dense beads to move easily to points of imbalance and dampen vibrational energy.
One method of introducing free-flowing tire balancing material into the tire casing is to pour the material into the tire casing during the installation of the tire onto the rim. Although this method is simple, it requires the tire to be dismounted from the rim, which normally occurs only during installation of a new tire, and, it is easy for the balancing material to adhere to the rim seat and prevent the tire from properly sealing against the rim.
Alternative methods are disclosed by Fogal et al. in U.S. Pat. No. 5,386,857 and U.S. Pat. No. 5,472,023. In these patents, a pulverulent material is introduced into a cylindrical chamber having axially spaced and radially offset inlets and outlets, subjecting the confined pulverulent material to pressurized air which is transformed into a cyclonic air current within the chamber by the radially offset inlet and outlet, and forcefully driving the admixed air/pulverulent material from the chamber into a tire through the associated tire valve stem.